m Ransley wrote:
Tioga, how could a roof cave in from a wet crawlspace ???

Yeah, that was a blooper. In my mother's case, the "contractor" was so
bad he SHINGLED a roof with 1/4" pitch. The whole addition was
situated beneath a huge deck he also put on to the house. By no means
did I want to give the impression that lack of drainage led to the roof
collapse.

However--and this is a big however--once water gets into anything
porous or even into masonry, osmotic "movement" will introduce H20 to
surprisingly heights in gypsum board and joists. Take my word for
it...my $22K+ word for it, you do NOT want to address drainage/flooding
problems after building is done.